1sys_sem.h(0P)              POSIX Programmer's Manual             sys_sem.h(0P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
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NAME

13       sys/sem.h — XSI semaphore facility
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SYNOPSIS

16       #include <sys/sem.h>
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DESCRIPTION

19       The <sys/sem.h> header shall define the following symbolic constant for
20       use as a semaphore operation flag:
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22       SEM_UNDO    Set up adjust on exit entry.
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24       The  <sys/sem.h>  header  shall define the following symbolic constants
25       for use as commands for the semctl() function:
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27       GETNCNT     Get semncnt.
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29       GETPID      Get sempid.
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31       GETVAL      Get semval.
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33       GETALL      Get all cases of semval.
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35       GETZCNT     Get semzcnt.
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37       SETVAL      Set semval.
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39       SETALL      Set all cases of semval.
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41       The <sys/sem.h> header shall define the semid_ds structure, which shall
42       include the following members:
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44           struct ipc_perm  sem_perm  Operation permission structure.
45           unsigned short   sem_nsems Number of semaphores in set.
46           time_t           sem_otime Last semop() time.
47           time_t           sem_ctime Last time changed by semctl().
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49       The <sys/sem.h> header shall define the pid_t, size_t, and time_t types
50       as described in <sys/types.h>.
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52       A semaphore shall be represented by an anonymous structure, which shall
53       include the following members:
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55           unsigned short  semval   Semaphore value.
56           pid_t           sempid   Process ID of last operation.
57           unsigned short  semncnt  Number of processes waiting for semval
58                                    to become greater than current value.
59           unsigned short  semzcnt  Number of processes waiting for semval
60                                    to become 0.
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62       The  <sys/sem.h>  header shall define the sembuf structure, which shall
63       include the following members:
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65           unsigned short  sem_num   Semaphore number.
66           short           sem_op    Semaphore operation.
67           short           sem_flg   Operation flags.
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69       The following shall be declared as functions and may also be defined as
70       macros. Function prototypes shall be provided.
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72           int   semctl(int, int, int, ...);
73           int   semget(key_t, int, int);
74           int   semop(int, struct sembuf *, size_t);
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76       In  addition,  the  <sys/sem.h>  header  shall  include the <sys/ipc.h>
77       header.
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79       The following sections are informative.
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APPLICATION USAGE

82       None.
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RATIONALE

85       None.
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FUTURE DIRECTIONS

88       None.
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SEE ALSO

91       <sys_ipc.h>, <sys_types.h>
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93       The System  Interfaces  volume  of  POSIX.1‐2008,  semctl(),  semget(),
94       semop()
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97       Portions  of  this text are reprinted and reproduced in electronic form
98       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
99       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
100       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
101       cal  and  Electronics  Engineers,  Inc  and  The  Open Group.  (This is
102       POSIX.1-2008 with the 2013 Technical Corrigendum  1  applied.)  In  the
103       event of any discrepancy between this version and the original IEEE and
104       The Open Group Standard, the original IEEE and The Open Group  Standard
105       is  the  referee document. The original Standard can be obtained online
106       at http://www.unix.org/online.html .
107
108       Any typographical or formatting errors that appear  in  this  page  are
109       most likely to have been introduced during the conversion of the source
110       files to man page format. To report such errors,  see  https://www.ker‐
111       nel.org/doc/man-pages/reporting_bugs.html .
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115IEEE/The Open Group                  2013                        sys_sem.h(0P)
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